Excessive airway secretions are a prominent feature of obstructive airway diseases characterized by airway inflammation. Respiratory mucus glycoproteins (MGP) are produced by at least two cell types in the respiratory tract. At least four mucin genes are expressed in the airway epithelium. These glycoproteins are relatively heterogenous in size; however, no specific characteristics are available for different MGP gene products. Therefore, quantitation of each specific mucin gene product has been difficult. Expression plasmids for the production of fusion proteins that contain a nonantigenic protein and a unique epitope from each of the known products are being developed for the purpose of developing enzyme-linked immunoabsorbent assays for measuring specific mucin gene products in culture media and in airway secretions.